Attenuating Ultra-Short Pulses in Coplanar Waveguide Modal Filters

This paper focuses on improving the attenuation of ultra-short pulses through modifications of boundary conditions of a coplanar waveguide modal filter (MF). This MF configuration includes two cutouts in the ground plane that create a mirrored conductor. Three variations of boundary conditions were studied, including a 50 Ω resistor at one end and a short circuit (SC) or open-circuit (OC), and SC-OC at the other end. The length of the prototype was 53 mm. Both quasistatic and electrodynamic simulations were performed to confirm measurement results. A Gaussian pulse with an amplitude of 1 V and a duration of 200 ps was excited to the MF input. By modifying the boundary conditions, the maximum attenuation achieved was 2.7 times half of the e.m.f. at the SC-OC configuration, with a corresponding bandwidth increasing up to 2.93 GHz. The measurement and simulation results were in good agreement. These findings demonstrate the potential for improved pulse attenuation using modified boundary conditions in a coplanar waveguide modal filter.